pythongh-117657: Make PyType_HasFeature (exported version) atomic (python#120484)

Make PyType_HasFeature (exported version) atomic

Author: Fidget-Spinner

Include/object.h

@@ -756,7 +756,11 @@ PyType_HasFeature(PyTypeObject *type, unsigned long feature)
     // PyTypeObject is opaque in the limited C API
     flags = PyType_GetFlags(type);
 #else
-    flags = type->tp_flags;
+#   ifdef Py_GIL_DISABLED
+        flags = _Py_atomic_load_ulong_relaxed(&type->tp_flags);
+#   else
+        flags = type->tp_flags;
+#   endif
 #endif
     return ((flags & feature) != 0);
 }

Objects/typeobject.c

@@ -3599,7 +3599,7 @@ type_init(PyObject *cls, PyObject *args, PyObject *kwds)
 unsigned long
 PyType_GetFlags(PyTypeObject *type)
 {
-    return type->tp_flags;
+    return FT_ATOMIC_LOAD_ULONG_RELAXED(type->tp_flags);
 }